Decreased T cell populations contribute to the increased severity of COVID-19.

Abstract Background We observe changes of the main lymphocyte subsets (CD16+CD56、CD19、CD3、CD4、and CD8) in COVID-19-infected patients and explore whether the changes are associated with disease severity. Methods One-hundred and fifty-four cases of COVID-19-infected patients were selected and divided into 3 groups (moderate group, severe group and critical group). The flow cytometry assay was performed to examine the numbers of lymphocyte subsets. Results CD3+, CD4+ and CD8 + T lymphocyte subsets were decreased in COVID-19-infected patients. Compared with the moderate group and the sever group, CD3+, CD4+ and CD8+ T cells in the critical group decreased greatly (P  Conclusions Reduced CD3+, CD4+, CD8+ T lymphocyte counts may reflect the severity of the COVID-19. Monitoring T cell changes has important implications for the diagnosis and treatment of severe patients who may become critically ill.